Preparation of silver salts in an organic liquid medium

ABSTRACT

Photographic silver halide salt compositions are formed in the presence of certain synthetic polymers in an organic solvent medium. In one aspect, silver halide grains having metal ions occluded therein can be made by this technique. In another aspect, inorganic silver halide slats made by this technique can be admixed with organic silver salts in an organic solvent and coated on a support to provide improved heat-developable photographic elements.

United States Patent [191 Lindholm et al.

[111 3,713,833 51 Jan. 30, 1973 [54] PREPARATION OF SILVER SALTS IN ANORGANIC LIQUID MEDIUM [75] Inventors: Robert Derwood Lindholm,

Rochester; Kenneth Robert Hollister, Pittsford, both of NY.

[73] Assignee: Eastman Kodak Company,

Rochester, NY.

[22] Filed: Oct. 28, 1970 [21] App1.No.: 84,923

[52] U.S.Cl. ..96/l14,96/114.1,96/1l4.6 [51] Int. Cl. ..G03c 1/04 [58]Field ofSearch ..96/114.1,114.6, 114

[56] References Cited UNITED STATES PATENTS 3,615,624 10/1971 Smith etal. 96/114 3,457,075 7/1969 Morgan et a1. ..96/114.6

2,717,833 9/1955 Wark ..96/108 3,003,879 10/1961 Priest et a1 2,311,0862/1943 Salo ..96/l 13 2,414,207 Lowe ..96/1 14 Primary Examiner-RonaldH. Smith AttorneyW. H. J. Kline, Bernard D. Wiese and Gerald E. Battist[57] ABSTRACT 9 Claims, No Drawings PREPARATION OF SILVER SALTS IN ANORGANIC LIQUID MEDIUM This invention relates to the preparation ofsilver salts and especially photographic silver salts. In one aspect,this invention relates to the precipitation or formation of silver saltsin an organic liquid medium in the presence of certain syntheticpolymers which are soluble in acetone. In another aspect, this inventionrelates to the precipitation of silver salts in an organic liquid mediumin the presence of vinyl copolymers comprising groups appendedtheretowhich contain thioether atoms and wherein said copolymer can bedissolved in acetone in concentrations of at least 3 percent, by weight,based on acetone. In another aspect, this invention relates to improvedprocesses for making silver halide grains tailored for specificphotographic applications such as heat-developable compositionscomprising inorganic silver salts and organic silver salts and alsocompositions containing silver halide grains having metal ions occludedtherein.

It is known in the art to prepare silver salts in the presence ofgelatin in an aqueous medium wherein the gelatin acts to peptize thesilver salt, preventing clumping of grains and providing somewhatuniform photographic properties throughout the silver halidecomposition. It is also known in the art to precipitate or form silversalt crystals in the presence of synthetic polymeric compounds which actas peptizers such as, for example, by procedures as disclosed in U.S.Ser. No. 701,084 by Smith et al. filed Jan. 29, 1968, now Pat. No.3,615,624, and U.S. Pat. Nos. 3,419,397 by Merrill and Perry issued Dec.31, 1968, 3,003,879 by Priest and Perry issued Oct. 10, 1961, 3,392,025by Whiteley and Perry issued July 9, 1968, and 2,752,246 by Weaverissued June 26, 1956. However, improved methods of forming silver saltsare desired which provide greater versatility in tailoring theparticular silver salts to specific photographic systems.

We have now found an improved process for preparing photographic silversalts in an organic liquid medium in the presence of certain syntheticpolymers which are more soluble in said organic liquid medium than inwater at the same temperature. Generally, the silver salts can beprepared in a medium which is substantially free of proteinaceouscompounds such as gelatin which has been commonly used in thepreparation of silver halide grains.

In one preferred embodiment, the synthetic polymer used in theprecipitation medium is a vinyl polymer comprising recurring unitshaving thioether groups appended thereto.

In another preferred embodiment, the silver salts of this invention areprecipitated in a medium wherein the liquid consists essentially oforganic liquids.

In another embodiment, said organic liquid is one which is miscible withwater and the silver salts are prepared in a mixture of water and thewater-miscible organic liquid.

In another embodiment, silver salt crystals are formed in an organicsolvent in the presence of a vinyl polymer comprising from 5 to 50 molepercent, and preferably from 10 to 30 mole percent, of recurring unitshaving thioether groups thereon;

In still another highly preferred embodiment, the synthetic copolymersused in the organic liquid mediurn for forming silver salts compriserecurring units having groups containing thioether groups and saidcopolymers can be further characterized as being 3% and preferably 5%,by weight, soluble in acetone at 25 C. and preferably are less than 3%,by weight, soluble in a water medium at a pH number less than 5 at 25 C.

The present process can be utilized for forming most silver saltsincluding, for example, the silver halides and the silver salts oforganic acids. In one preferred embodiment, the process is used toprecipitate grains or crystals of inorganic silver salts such as silverbromide grains, silver chloride grains, silver iodide grains, silverchlorobromide grains, silver chlorobromoiodide grains and the like.

Theorganic solvents referred to herein are those compounds which aresolvents for the polymeric compounds used in the precipitation medium.The term organic solvent generally refers to those compounds comprisingcarbon atoms and generally hydrogen atoms which generally have boilingpoints below 165 C. and preferably lower than about C. In certainpreferred embodiments of this invention, the polymers are soluble inorganic solvents such as alcohols, ketones, amides, nitriles, ethersincluding the cyclic ethers, and the like. Other solvents such asorganic acids, organic sulfoxides and organic sulfones can also be used,including mixtures of any of the above organic solvents. Typical usefulorganic solvents include acetone, dimethylformamide, methyl alcohol,ethyl alcohol, n-propyl alcohol, isopropyl alcohol, dioxane,dimethylsulfoxide, sulfolane, acetonitrile, tetrahydrofuran,dimethylacetamide, 1,2-dimethoxyethane, acetic acid, triethylamine, andthe like. Of course, in those embodiments wherein water is also presentduring the precipitation step, the organic liquid is preferablywater-miscible.

In one preferred embodiment of this invention, the synthetic polymerspresent during the precipitation comprise recurring units therein havinggroups appended thereto which have thioether or sulfide-sulfur atomstherein. In a preferred embodiment, the units of this type are derivedfrom monomers of amides and esters of ethylenically unsaturated acids,including maleic acids, acrylicacids, methacrylic, acids and the like,in which the respective amine and alcohol condensation residues in saidamides and esters contain at least one organic group having at least onesulfide-sulfur atom linking two methylene groups (CH Typical units ofthis type useful in certain embodiments according to this invention aredisclosed in U.S. Ser. No. 701,084 filed Jan. 29,1968, which isincorporated hereinby reference. These units can be obtained frommonomers suchas:

N-(3-thiabutyl)acrylamide N-(3-thiapentyl)acrylamide IN-(4-methyl-2-thiapentyl)acrylamideN-(2,5-dimethyl-4-thiahexyl)acrylamide N-(5-thiaheptyl)acrylamideN-(4-thiaheptyl)acrylamide N-(6-methyl-4-thiaheptyl)acrylamideN-(3-thiaoctyl)acrylamide N-(7-thianonyl)acrylamideN-(6-ethyl-2-methyl-4-thiaoctyl)acrylamideN-(6-thia-2,4,9-trimethyldecyl)acrylamide N-(4-thia'dodecyl)acrylamide3-thiapentyl acrylate Bis(2-thiabutyl)methyl acrylate methylthioethylacrylate methacryloylprolylmethionine methyl ester The useful syntheticpolymers also generally include recurring units of alkyl acrylates. Thealkyl acrylates used in making the copolymers of this invention aregenerally referred to as unsubstituted acrylic esters (which formhydrophobic units when polymerized) and, of course, include the alkylmethacrylates, as well as the alkylv acrylates. Typical useful acrylicesters include methyl acrylate, ethyl acrylate, propyl acrylate, butylacrylate, isopropyl acrylate, isobutyl acrylate, tbutyl acrylate, therespective methacrylates, and the like. Preferably, the alkyl acrylateis a simple compound such as methyl acrylate or methyl methacrylate.

The interpolymers of this invention can be generally polymerized bysolution polymerization, emulsion polymerization or bulk polymerizationprocedures, but they are preferably polymerized by solutionpolymerization procedures. The polymerization is carried out to obtain amolecular weight of the interpolymer of at least about 10,000 to about500,000 and preferably from about 30,000 to about 100,000. The inherentviscosities of the interpolymers generally range from about 0.1 to about2.

The copolymers used in the process of this invention generally are thosewhich comprise from about toabout 50, and preferably from about to about30, mole percent of recurring units having groups appended thereto whichhave thioether or sulfide-sulfur atoms therein. Typical usefulcopolymers can be further characterized as being at least 3 percentpreferably at least about 5 percent, by weight, soluble in acetone at C.Moreover, the useful polymers are generally less then 3 percent solublein water at 25 C. which has been adjusted to a pH number of less than 5.As a result, units which contain highly ionizable groups such as, forexample, units containing sulfonic acid groups as3-acryloxypropane-l-sulfonic acid sodium salt can be tolerated in onlyminor amounts such as mole percents of less than 10 percent, andpreferably the useful copolymer is substantially free of unitscomprising sulfoxy groups (i.e., sulfur-oxygen groups). On the otherhand, units such as those derived from acrylic acid which has a lowionization constant can be tolerated in much larger amounts. Thecopolymers of this invention can, of course, and generally do containunits which are regarded as being hydrophobic or neutral as long as thesolubility of the copolymer can be characterized as defined above.

The silver salts prepared according to this invention can be sensitizedwith chemical sensitizers, such as with reducing agents; sulfur,selenium or tellurium compounds; gold, platinum or palladium compounds;or combinations of these. Suitable procedures are described, forexample, in US. Pat. Nos. 1,623,499 of Sheppard issued Apr. 5, 1927,2,399,083 of Waller et a]. issued Apr. 23, 1946, 3,297,447 of McVeighissued Jan. l0, 1967, and 3,297,446 of Dunn issued Jan. 10, 1967.

Photosensitive, silver salt compositions prepared according to thisinvention can be protected against the production of fog and can bestabilized against loss of sensitivity during keeping. Suitableantifoggants and stabilizers, e.g., used alone or in combination,includefor example, thiazolium salts; azaindenes; mercury salts asdescribed,for example, in US. Pat.No. 2,728,663 of' in one preferred embodiment ofthis invention, a

support is provided with coatings thereon of a light-stable organicsilver-salt oxidizing agent, an organic reducing agent and aphotosensitive, inorganic, silver salt, preferably silver halide, whichprovides a photographic and thermographic element. A visible image inthe photographic element can be produced within a few seconds afterimagewise exposure by heating the element to moderately elevatedtemperatures, e.g.,

about 80 to about 250 C.

The photographic and thermographic elements com prise the inorganicsilver salt in admixture with the organic silver salt. A typicalconcentration range of the described photosensitive silver halideprepared in the,

process of the invention is from about 0.005 to about. 0.50 mole ofsilver salt per mole of silver salt of organic acid, e.g., per mole ofsilver behenate. Preferred inorganic silver salts are photosensitivesilver halides, e.g., silver chloride, silver bromide, silverchlorobromide, silver iodide, silver bromoiodide, silver chloroiodide,silver chlorobromoiodide, or mixtures thereof. The photosensitive silverhalide can be coarseor finegrain; in one embodiment, the very fine-grainsilver halides are especially useful.

The photographic and thermographic elements comprise an oxidizing agent,especially a silver salt of anorganic acid. The silver salt of theorganic acid should be resistant to darkening under illumination toprevent undesired deterioration of a developed image. An especiallysuitable class of silver salts of organic acids is.

represented by the water-insoluble silver salts of longchain fatty acidswhich are stable to light. Compounds which are suitable silver saltsinclude silver behenate, silver stearate, silver oleate, silver laurate,silver hydroxystearate, silver caproate, silver myristate and' salts canbe employed, if desired, in place of the silver salts such as zincoxide, gold stearate, mercuric behenate, auric behenate and the like,but silver salts are preferred.

Organic reducing agents can be employed in certain embodiments of thedescribed thermographic composition and/or element which include, forexample, substituted phenols and naphthols. The bis-naphthol which ispreferred is a bis-B-naphthol of the formula:

wherein R and/or R are hydrogen, alkyl containing one to three carbonatoms, alkoxy, e.g., alkoxy containing one to two carbon atoms such asmethoxy or ethoxy, halogen, nitro, amino or a diazonium halide salt, andn is or 1. Suitable bis-B-naphthols which can be employed in thepractice of the invention include:

2,2 '-dihydroxyl ,l -binaphthyl, 6,6'-dibromo-2,2'-dihydroxy-l ,l'-binaphthyl, 6,6'-dinitr0-2,2-dihydroxy-l ,l '-binaphthyl and/orbis-(2-hydroxy-l-naphthyl)methane. The described reducing agents aresuitable in a range of concentration; however, they are especiallysuitable at a concentration from about 0.10 to about 0.75 mole ofreducing agent per mole of oxidizing agent. I Other reducing agents,which are typically silver halide developing agents, can be used aloneor in conjunction with the above bis-naphthol reducing agents. Suitablesilver halide developing agents include, for example,polyhydroxybenzenes such as hydroquinone developing agents, e.g.,hydroquinone, alkyl-substituted hydroquinones as exemplified by tertiarybutylhydroquinone, methylhydroquinone, 2,5-dimethylhydroquinone and2,6-dimethylhydroquinone; catechols and pyrogallol; halo-substitutedhydroquinones such as chlorohydroquinone or dichlorohydroquinone;alkoxy-substituted hydroquin- -ones such as methoxyhydroquinone orethoxyhydroquinone; methylhydroxynaphthalene; phenylenediaminedeveloping agents; methylgallate; aminophenol developing agents such as2,4-;

diaminophenols and methylaminophenols; ascorbic acid developing agentssuch as ascorbic acid, ascorbic acid ketals and ascorbic acidderivatives such as those described in US. Pat. No. 3,337,342 of Greenissued Aug. 22, 1967; hydroxylamine developing agents such as N ,N-di-(2-ethoxyethyl)hydroxylamine; 3- pyrazolidone developing agents suchas l-phenyl-3- pyrazolidone and 4-methyl-4-hydroxymethyl-l-phenyl'3-pyrazolidone including those described in British Pat.

No. 930,572 published July 3, 1963; hydroxytetronic 5 wherein R ishydrogen, hydroxyl or a metal ion such as potassium, sodium, lithium,silver,gold or mercury; Z, represents atoms completing a heterocyclicnucleus, especially a 5- or 6-member heterocyclic nucleus. The atomscompleting the heterocyclic nucleus can be, for example,

or an alkylene group containing three or four carbon atoms. The atomscompleting the heterocyclic nucleus can contain various substituentgroups such as amino, alkyl amino, e.g., methylamino or ethylamino,hydroxyl, carbamyl and the like. An especially suitable activator-toningagent is a heterocyclic activator-toning agent containing at least onenitrogen atom which is preferably a cyclic imide of the formula:

wherein R is hydrogen, hydroxyl or a metal ion such as potassium,sodium, lithium, silver, gold or mercury; Z represents carbon atoms of aseries completing a cyclic imide nucleus, typically consisting of fromfive to six carbon atoms, e.g., a phthalimide or succinimide nucleus.The atoms of the cyclic imide nucleus can contain various substituentgroups, especially amino, alkyl, such as alkyl containing one to fivecarbon atoms, such as methyl, ethyl, propyl, butyl or pentyl or aryl,such as aryl containing six to 20 carbon atoms, such as phenyl, tolyland xylyl. Suitable activator-toning agents which can be employed in thepractice of the invention include, for instance, phthalimide,N-hydroxyphthalimide, N-potassium phthalimide, N-silver phthalimide,N-mercury phthalimide, succinimide and/or N-hydroxysuccinimide. Thedescribed activator-toning agents are suitable in a range ofconcentration; however, they are especially suitable at a concentrationfrom about 0.10 mole to about 1.05 moles of activator-toning agent permole of oxidizing agent.

Other so-called activator-toning agents can be em- 0 ployed incombination with other components of the described photographic andthermographic element in the practice of the invention. Variousso-called toners can be employed for this purpose. Typica ly, aheterocyclic organic toning agent containing at least two hetero atomsin the heterocyclic ring of which at least one is a nitrogen atom isemployed. These are described, for example, in US. Pat. No. 3,080,254 ofGrant issued Mar. 5, 1963. Suitable toners include, for example,phthalazinone, 2-acetylphthalazinone and 2- phthalylphthalazinone. Othersuitable toners are described, for example, in US Pat. No. 3,446,648 ofWorkman issued May 27, 1969.

In another preferred embodiment, the procedures of this invention areused to prepare silver halide grains having polyvalent metal ionsoccluded therein. Generally, the organic medium permits greaterversatility in incorporating metal ions in the silver halide Analysiscalculated for C ,H, O S: 54.8% C, 7.0% 1-1, 3.5% S.

Found: 54.6% C, 7.1% H, 3.3% S.

Example 3: Preparation of copoly(3-thiapentyl acrylate-ethylacrylateacrylic acid) (mole ratio 1:623)

A flask is charged with a solution of 16.0 g. (0.10 mole) of3-thiapentyl acrylate, 60.0 g. (0.60 mole) of ethyl acrylate, 21.6 g.(0.30 mole) of acrylic acid and 0.48 g. of2,2-azobis(2-methylpropionitrile) in 390 ml. of acetone. After purgingthe solution with nitrogen for minutes, it is heated to 60 C. under areflux conthis invention, improved heat-stabilization properties andimage characteristics are observed when elements containing theseemulsions are processed by the procedure of Colt, U.S. Pat. No.3,418,122 issued Dec. 24, 1968. Of course, additional polyvalent metalions may be added to emulsions containing grains having occludedpolyvalent metal ions therein prepared in accordance with this inventionin the same manner as for emulsions prepared in the presence of gelatin;polyvalent metal ion salts, such as lead salts,rho.dium salts and thelike, generally promote heat stabilization of silver halide emulsionsand improve image characteristics upon chemical development and heatdevelopment.

The invention can be furtherillustrated by the following examples ofpreferred embodiments thereof. Example 1: Preparation ofcopoy(3-thiapentyl acrylate ethyl acrylate) mole ratio 1:9)

A flask is charged with a solution of 8.0 g. (0.05 mole) of 3-thiapentylacrylate, 45.0 g. (0.45 mole) of ethyl acrylate and 0.27 g. of2,2'-azobis(2-methylpropionitrile) in 250 ml. of acetone. After purgingthe solution with nitrogen for 10 minutes, it is heated to 60 C. under areflux condenser overnight. A clear, colorless, viscous dope resultswhich is found to contain 21.7% solids. The dope is used directlywithout further purification.

A portion of another sample prepared in the same manner is poured slowlyinto a large excess of a 1:1 (vol.) mixture of methanol and water withstirring. The slightly sticky, rubbery, white polymer which precipitatesis thoroughly washed-in the same nonsolvent mixture and dried undervacuum. A sticky, colorless product is obtained which has aninherentviscosity in acetone of 0.66.

Analysis calculated for C H O S: 58.8% C, 8.0% H, 3.0% S. I

Found: 58.4% C, 7.5% 1-1, 2.9% S.

Example2: Preparation of copoly(3-thiapentyl acrylate ethyl acrylateacrylic acid) (mole ratio 1:4:5)

A flask is charged with a solution of 16.0 g. (0.10 mole) of3-thiapentyl acrylate, 40.0 g. (0.40 mole) of ethyl acrylate, 36.0 g.(0.50 mole) of acrylic acid and 0.46 g. of2,2'-azobis(Z-methylpropionitrile) in 360 ml. of acetone. After purgingthe solution with nitrogen for 10 minutes, it is heated to 60 C. under areflux condenser overnight. A clear, colorless, viscous dope resultswhich is found to contain 25.6% solids. I

- A small portion of the dope is poured slowly into a large excess of a1:1 (vol.) mixture of methanol and water with stirring. The sticky,rubbery product which precipitates is thoroughly washed in the samenonsolvent mixture and dried under vacuum. It is found to have aninherent viscosity in acetone of 0.90.

denser overnight. A clear, colorless, viscous dope results which isfound to contain 25.4% solids.

A small portion of the dope is poured slowly into a I large excess of a1:1 (vol.) mixture of methanol and water with stirring. The sticky,rubbery product which precipitates is thoroughly washed in the samenonsolvent mixture and dried under vacuum. It is found to have aninherent viscosity in acetone of 0.97.

Analysis calculated for C H O S: 56.5% C, 7.4% H, 3.3% S.

Found: 55.6% C, 8.0% 1-1, 3.1% S.

Example 4: Preparation of copoly( 3-thiapentyl acrylate butyl'acrylate)(moleratio 1:6)

A flask is charged with a solution of 72.0 g. (0.45 mole) of.3-thiapentyl acrylate, 345.6 g. (2.70 moles) of butylf acrylate and 1.25g. of 2,2'-azobis(2-methy1- propionitrile) in 1600 ml. of p-dioxane. Thesolution is purged with nitrogen for 20 minutes and then heated to 60 C.under a blanket of nitrogen overnight. The clear, colorless, viscousdope which results is poured slowly intoa large excess of a 3:2 (vol.)mixture of methanol and water with stirring. The sticky white polymerwhich precipitates is thoroughly washed in 3:1 (vol.) mixture ofmethanol and water. It is dried under vacuum yielding 406.7 "g. (98%yield) of a sticky, colorless polymer. The product has an inherentviscosity in acetone of 0.31.

Analysis calculated for C H O S: 63.3% C, 9.1% H,

Found: 62.8% C, 8.8% 11, 3.3% S.

Example 5: Preparation of AgBr grains in the presence ofcopoly[S-thiapentylacrylate ethyl acrylate] (mole ratio 1:9)

To a mixture of 2 g. copoly[3-thiapentylacrylate for each solution is19.4 ml. per minute.

After the addition, hexane is added to precipitatecopoly[3-thiapentylacrylate et'nyl acrylate], AgBr, and LiClO Theundesirable I..iClO is then removed by adding ethanol and decanting,leaving the gummy emulsion, which is redispersed in 30 ml. acetone.Example 6: Preparation of AgBr grain incorporating Au To a solution of-19 ml. acetone,'2 g. of copoly[3- thiapentylacrylate ethyl acrylate](mole ratio 1:9), and 1 ml. of 0.0001M KAuBr, in acetone are addedsimultaneously 20 ml. of 0.25M AgClO, solution in acetone and 20 ml. of0.25M LiBr solution in acetone. The reaction temperature is 23 C., andthe constant rate of addition for each solution is 19.4 ml. per minute.

' phthalimide (1% in acetone) After the addition, hexane is added andthe supernatant liquid is poured off. The precipitate is washed severaltimes with ethanol to remove the LiClO The emulsion remaining isredispersed in 30 ml. acetone. The emulsion is then hand-coated on afilm base with and without a halogen acceptor and tested for print-outby exposing seconds to photoflood through a step wedge with 0.3 log Esteps. The coating without the halogen acceptor shows about one step ofprint-out while the coating containing the halogen acceptor shows sixsteps of print-out.

Example 7:

A light-sensitive silver halide photographic emulsion is prepared.Silver perchlorate (AgClO is added to an acetone solution in sufficientamount to result in a concentration of 10 molar. In a similar manner,lithium bromide (LiBr) is added to an acetone solution in quantitiessufficient to result in a concentration of 10 molar. A third solution isprepared by dissolving copoly[3-thiapentylacrylateethyl acrylate] (moleratio 1:9) in acetone.

Equal volumes of the silver salt and halide compound solution are addedat a controlled flow rate to the third solution with rapid agitation. Afine-grain silver halide emulsion results. Table 1 describes severalphotographic emulsions which are prepared according to the method ofthis example. Table 1 further describes variations in preparation ofeach of the emulsions.

"copolyl3-thiapentyl acrylate-ethyl acrylate] (mole ratio 1:9)

Example 8;

Several light-sensitive photographic materials are prepared containingthe following components:

silver behenate (50 mg.lm1. in acetone) 2.0 ml. behenic acid (200mg./ml. in acetone) 0.5 ml. poly(vinyl butyral) (60 mg./ml. in acetone)0.5 ml.

These components are dispersed with an ultrasonic probe and thefollowing materialsare then added:

silver halide emulsion (from Table 1; level described in Table 2)3-carboxymethyl-5-[(3-mcthyl-2(3)-thiazolinylidene)isopropylidenelrhodanine (7 mgJml. in acetone-methanol)2.0 ml. 1,1 '-bi-2-naphthol (3% in acetone) 2.0 ml. 2.0 ml.

The above photographic mixtures are coated on a resin-treatedphotographic paper support at a wet thickness of 0.004 inch. Table 2will describe the lightsensitive silver halide photographic emulsionused in each coating.

' TABLE 2 Coating AgBr emulsion used Level of AgBr Coated (mg/ft) 1 A1.0 2 B 1.0 3 -C 0.5 4 -D 0.5 5 -E 1.0 6 F 1.0

Samples of the coatings of this example are exposed to a line copy for5.0 seconds on a Kodak Verifax copier. The exposed samples areheat-processed on a curved hot block for 5-10 seconds at a temperatureof 140 C. in each case the samples produce a visible line image.

Example 9:

A light-sensitive silver halide photographic emulsion is prepared.Silver perchlorate (AgClO is added to acetone in sufficient quantity toresult in a concentration of 10- molar. Similarly, lithium bromide(LiBr) is added to acetone in amounts sufficient to result in aconcentration of 10" molar. A third solution is prepared by dissolving50.0 g. of copoly[3-thiapentyl acrylate ethyl acrylate acrylic acid](mole ratio 124:5) per mole of silver bromide in 25.0 ml. of acetone.

When all solutions have been prepared, equal volumes of the silver saltand lithium bromide solutions are added at a controlled rate of flow 2.0ml. per minute) tothe thirdsolution containing the copolymeric silverhalide peptizer. A fine-grain silver bromide photographic emulsionresults.

Example 10:

The procedure set out for the production of the finegrain,light-sensitive, silver bromide, non-gelatin emulsion of Example 9 isrepeated with the exception that copoly[3-thiapentyl acrylate ethylacrylate acrylic acid] (mole ratio 1:6:3) is substituted for copoly[3-thiapentylacrylate ethyl acrylate acrylic acid] (mole ratio 1:4:5).

Example 11:

The procedure set out for the production of the finegrain,light-sensitive, silver bromide, non-gelatin, photographic emulsion ofExample 9 is repeated with the exception that copolyl3-thiapentylacrylate nbutyl acrylate] (mole ratio 1:6) is substituted forcopoly[3-thiapentyl acrylate ethyl acrylate acryl' ic acid] (mole ratio1:425).

Example 12:

Several photosensitive and thermosensitive elements are prepared bycoating the following composition on a suitable photographic papersupport at a wet thickness of 0.004 inch.

silver emulsion (preparations described in Table 3 describes thespecific silver bromide photographic emulsion employed in each of theelements of this example. Table 3 further gives a visual analysis of thephotographic images which result from exposing samples of thephotographic and thermographic elements of this example to a tungstenlight source for several seconds and heat-processing the exposed samplesfor about 5-15 seconds on a curved hot block whose temperature is about120 1 30 C.

Example 13: (comparison) A coating composition is prepared by mixing thefollowing components:

silver behenate 42.0 g. behenic acid 32.0 g. polyvinyl butyral 15.0 g.silver bromide (prepared ex situ in the absence a peptizer) 0.45 g.phthalimide 8.5 g. acetone-toluene (1:1 parts by volume) 500 ml.

After ball-milling for 18 hours, 141 ml. of the resulting dispersion iscombined with the following-solutions:

acetone containing 0.08% by weight 3-ethyl-5-[(3-ethyl-2(3H)-benzothiazolylidene)isopropylidene]-2-thio-2,4( 3 ,5)-oxamlidenedione 4.4 ml. acetone containing 6.25% by weight 2,2-

dihydroxy-l ,l '-binaphthy 52.5 ml.

The composition is mixed and then coated on a suitable resin-coatedpaper support at a wet thickness of 0.004 inch and dried.

The photosensitive element is placed into contact with an originaltransparent film containing a developed image and exposed for 5 secondsby a 100- watt lamp at a distance of 1 foot. The photosensitive elementis separated from the original and the resulting latent image isdeveloped by holding the element in contact with, a curved metal blockfor seconds at 120 C. A very faint but distinguishable image resultscompared with the elements made in accordance with Examples 9 and 10wherein the inorganic silver halide is prepared in the presence silverhalide peptizer.

Although the invention has been described in considerably detail withparticular reference to certain preferred embodiments thereof,variations and modifications can be effected within the spirit and scopeof the invention.

We claim:

1. In a process of forming silver halide salt crystals in anorganic-solventhaving a boiling point below 165 C, the improvementcomprising forming 'said crystals in said organic solvent in thepresence of a synthetic polymeric compound which is a yinyl copolymercomprising (l) recurring units having groups appended thereto whichcontain thioether moieties or sulfide-sulfur atoms therein and (2)recurring units of an alkyl acrylate.

2. A process according to claim 1 wherein said copolymer comprises fromabout 5 to about 50 mole percentof said recurring units having groupsappended thereto which contain thioether or sulfide-sulfur atomstherein.

3. A process according to claim 1 wherein said copolymer ischaracterized as being at least 3 percent, by weight, soluble in acetoneat 25 C.

4. A process according to claim 1 wherein said silver salt crystals areformed-in the presence of polyvalent metal ions.

5. A process according to claim 1 wherein said silver salts are formedin the presence of trivalent or of a polymer which is a tetravalentmetal ions.

6. A photographicelement comprising (1) a support and (2) at least onelayer thereon comprising anorganic silver salt in admixture with aninorganic silver halide salt which has been formed in an organic solventhaving a boiling point below C in the presence of a synthetic vinylcopolymer comprising (a) recurring units having groups appended theretowhich contain thioether moieties or sulfide-sulfur atoms therein and (b)recurring units of an alkyl acrylate.

7. A photographic element according to claim 6 wherein said syntheticvinyl copolymer is at least 3%, by weight, soluble in acetone and lessthan 3%, by weight, soluble in water at 25 C. ata pl-l number less thanabout 5.

8. A photographic element according to claim 6 wherein said syntheticvinyl copolymer is copoly(3- thiapentyl acrylate ethyl acrylate).

9. A photographic element according to claim 6 wherein said syntheticvinyl copolymer is copoly(3- thiapentyl acrylate ethyl acrylate 5-acrylic acid).

l t l

1. In a process of forming silver halide salt crystals in an organicsolvent having a boiling point below 165* C, the improvement comprisingforming said crystals in said organic solvent in the presence of asynthetic polymeric compound which is a vinyl copolymer comprising (1)recurring units having groups appended thereto which contain thioethermoieties or sulfide-sulfur atoms therein and (2) recurring units of analkyl acrylate.
 2. A process according to claim 1 wherein said copolymercomprises from about 5 to about 50 mole percent of said recurring unitshaving groups appended thereto which contain thioether or sulfide-sulfuratoms therein.
 3. A process according to claim 1 wherein said copolymeris characterized as being at least 3 percent, by weight, soluble inacetone at 25* C.
 4. A process according to claim 1 wherein said silversalt crystals are formed in the presence of polyvalent metal ions.
 5. Aprocess according to claim 1 wherein said silver salts are formed in thepresence of trivalent or tetravalent metal ions.
 6. A photographicelement comprising (1) a support and (2) at least one layer thereoncomprising an organic silver salt in admixture with an inorganic silverhalide salt which has been formed in an organic solvent having a boilingpoint below 165* C in the presence of a synthetic vinyl copolymercomprising (a) recurring units having groups appended thereto whichcontain thioether moieties or sulfide-sulfur atoms therein and (b)recurring units of an alkyl acrylate.
 7. A photographic elementaccording to claim 6 wherein said synthetic vinyl copolymer is at least3%, by weight, soluble in acetone and less than 3%, by weight, solublein water at 25* C. at a pH number less than about
 5. 8. A photographicelement according to claim 6 wherein said synthetic vinyl copolymer iscopoly(3-thiapentyl acrylate - ethyl acrylate).